Optimization of network signaling load and/or user equipment power consumption in a packet mobile system

ABSTRACT

In an embodiment, there is provided a method for optimization of network signalling load and/or User Equipment power consumption in a packet mobile system wherein an User Equipment UE has access to a network comprising a Core Network CN accessed by a Radio Access Network RAN, a method wherein CN assistance information is provided by said CN to said RAN for an UE, said CN assistance information including information determined in said CN based on a learning by said CN of a traffic pattern and/or a mobility pattern of said UE, and said CN assistance information is used in said RAN to adjust RAN parameters enabling to control transitions between idle and connected state and/or power consumption in connected state for said UE.

The present invention generally relates to mobile communication networks and systems.

Detailed descriptions of mobile communication networks and systems can be found in the literature, such as in particular in Technical Specifications published by standardization bodies such as for example 3GPP (3^(rd) Generation Partnership Project).

In general, in such systems, an User Equipment (UE) has access to a mobile network comprising a Core Network (CN) accessed by a Radio Access Network (RAN).

Examples of packet mobile communication systems include EPS (Evolved Packet System), UMTS, . . . etc.

EPS network, for example, comprises a Core Network called EPC (Evolved Packet Core) that can be accessed by a Radio Access Network called E-UTRAN. An example of architecture of EPS network is recalled in FIG. 1 (taken from 3GPP TS 23.401), showing the main network nodes and interfaces between network nodes. Interfaces between EPS network nodes include, in particular, Uu interface between UE and E-UTRAN node called eNodeB (eNB), and S1-MME interface between eNB and EPC node called Mobility Management Entity (MME).

Control plane signaling may be exchanged on the Uu interface between UE and eNB, and on the S1-MME interface between eNB and MME, during signaling procedures. Signaling procedures include, in particular, signaling procedures performed at UE state transition (such as service request procedure performed at transition from idle to connected state, or signaling connection release procedures performed at transition from connected to idle state), mobility procedures (such as handover procedure performed in UE connected state, or Tracking Area Update procedure performed in UE idle state). An UE may transition from connected state to idle state if there is not enough UE activity in the user plane, or from idle to connected state if there is again UE activity in the user plane. RRC signaling protocol between UE and eNB is defined in particular in 3GPP 36.331. S1-AP signaling protocol between eNB and MME is defined in particular in 3GPP TS 36.413.

New types of communications, such as Machine Type Communication (MTC) or other mobile data applications communications (e.g. Instant Messaging IM, social networking applications, . . . etc.) are becoming increasingly used. Such new types of communications have new service requirements, such as frequent small data transmission, frequent UE state transitions, . . . etc. New functionalities are therefore needed for the support of such new service requirements, such as functionalities to efficiently support increased control plane signaling with minimal impact on the network and on the UE power consumption, . . . etc. More generally, network and system optimizations are needed for such new types of communications.

Embodiments of the present invention in particular address such needs.

These and other objects are achieved, in one aspect, by a method for optimization of network signalling load and/or User Equipment power consumption in a packet mobile system wherein an User Equipment UE has access to a network comprising a Core Network CN accessed by a Radio Access Network RAN, a method wherein CN assistance information is provided by said CN to said RAN for an UE, said CN assistance information including information determined in said CN based on a learning by said CN of a traffic pattern and/or a mobility pattern of said UE, and said CN assistance information is used in said RAN to adjust RAN parameters enabling to control transitions between idle and connected state and/or power consumption in connected state for said UE.

These and other objects are achieved, in other aspects, by entities configured to carry out such method, said entities including, in particular (though not exclusively), RAN entity (such as eNB for E-UTRAN, or RNC for UMTS), CN entity in charge of control plane (such as MME for EPC, or SGSN for UMTS), CN entity in charge of user plane (such as Serving Gateway S-GW or PDN Gateway P-GW for EPC, or GGSN for UMTS).

Some embodiments of apparatus and/or methods in accordance with embodiments of the present invention are now described, by way of example only, and with reference to the accompanying drawings, in which:

-   -   FIG. 1 is intended to recall an example of architecture for EPS         network,     -   FIG. 2 is intended to recall an example of timing for an UE         experiencing frequent idle-active mode transitions,     -   FIG. 3 is intended to illustrate, in a simplified way, an         example of procedure based on the use of CN assistance         information according to embodiments of the present invention.

Embodiments of the present invention will be more detailed in the following, by way of example for 3GPP systems such as EPS. However it should be understood that the present invention is not limited to EPS, and could apply as well to systems other than EPS (for example UMTS, or systems specified by standardization bodies other than 3GPP).

3GPP SA2 is in the process of studying enhancements for machine-type and other mobile data applications communications (3GPP release 12, see 3GPP TR 23.887). Many mobile data applications (e.g. always on mobile data applications such as IM or social networking applications, etc.) are characterized in particular by transmission of small and bursty data packets (i.e. in terms of packet size) in the UL and DL, e.g.

-   -   status update messages to notify the users of status updates         relating to the application, e.g. applications such as FindMe         generate status update messages upon geographic position changes         up to every 60 seconds;     -   periodic keep-alive messages to keep the application session         alive and also to avoid the expiry of NAT mapping which causes         IP session disconnection,     -   presence information of buddies in an IM buddy list,     -   update of user location upon user “check in”,     -   update of “Facebook likes” to a user's friends, etc.

Bursty data transmission may cause the UE to transition frequently between idle and connected state, if the UE is sent to idle mode soon after the transmission of the data is complete. If the UE is kept in connected mode for an extended duration it has impact on UE power consumption and more extensive control plane signalling is required for handovers. This is depicted e.g. in FIG. 2 corresponding to FIG. 2 of 3GPP TR 22.801 (non-MTC Mobile Data Applications impacts) clause 5.2.

Such frequent transmissions can have the following adverse effects on the network and the UE:

-   -   Increased control plane signalling in RAN (Radio Access Network)         and CN (Core Network);     -   Increased UE power consumption.

RAN2 studies in 3GPP TR 36.862 analyse in particular the effects of the RRC inactivity release timer & the DRX (Discontinuous Reception) cycle on network signalling (transitions idle<>connected), handovers (extra handover signalling when keeping the UE in connected state for a longer RRC release timer, in particular for moving UEs), and UE power consumption, for different kinds of traffic. RAN2 also specified in Rel-11 (see 3GPP TS 36.300 and 36.331) a new UE assistance information procedure enabling the UE to indicate to the network a power preference indication, e.g. lower power consumption, to enable the eNB to optimize the setting of the DRX parameter & RRC (inactivity) release timer.

Solutions are now being investigated in 3GPP SA2 to reduce the high frequency of signalling procedures, e.g. RRC signalling, paging/service request procedures, caused by bursty data transmissions or frequent UE state transitions.

S2-122787 (NEC, 3GPP SA2#92) proposed to monitor the traffic of the user (using a monitoring client in the UE and a monitoring server in the PLMN) to learn the traffic patterns of the user, store them in the HSS and re-use them to optimize the user inactivity timer used in the RAN. But the solution based on determination of individual application traffic patterns is complex to design & deploy, requires UE changes (traffic monitoring client in the UE) and thus cannot be used with legacy terminals, and further contribute to load the radio and core network by requiring the UE to send extra traffic to the monitoring server in the PLMN and requiring the latter to upload the traffic patterns in the HSS.

Other solutions are being studied to minimize the number of keep-alive messages the terminal sends e.g. by coordinating keep-alive messages across all the applications running on the UE or by delegating some keep-alive control to the network. Although this will help reducing the frequency of bursty data transmission for some applications, this will not help for frequent bursty data transmissions caused for other reasons e.g. status updates, user location updates, presence information updates . . .

Embodiments of the present invention in particular enable to avoid such drawbacks or solve such problems.

In an embodiment, the Packet Switched Core Network (and in particular the Mobility Management Control entities i.e. MME and SGSN) can provide assistance information to the radio access network (eNB for E-UTRAN and RNC for UTRAN) based on the learning of the traffic pattern (e.g. time between successive signaling connections, mobile originated or/and mobile terminated traffic) and/or the mobility pattern (e.g. static/nomadic vs moving user) of the user and/or user's subscription parameters (e.g. static/nomadic user), that enables the RAN to adjust/optimize the RAN parameters (DRX cycle, RRC user inactivity timer) applied to the user and thus reduce the frequency of transitions between idle and connected states, minimize network signaling and save UE battery.

In an embodiment, the Mobility Management Control entities (i.e. MME and SGSN) are well aware of when signaling connections are established and released with the UE/RAN and can make use of this to monitor e.g.

-   -   the time elapsed between the release of the last signaling         connection and the establishment of the subsequent signaling         connection. A short duration (e.g. a few seconds) would be an         incentive for the RAN to increase the RRC user inactivity timer;     -   the frequency of transitions between idle and connected modes,         and detect offending UEs with abnormally frequent transitions;     -   whether or how frequently the traffic originates from the UE         or/and the network, e.g. whether this is an UE that only or         mainly utilize mobile originated communications. UEs with Mobile         originated only traffic or Infrequent mobile terminated traffic         could be configured e.g. with a longer DRX period to minimize         battery usage (since this would not add the adverse effect of         adding latency for delivery of mobile terminated traffic).

In an embodiment, the MME and SGSN can subsequently use these informations to pass information assisting the RAN (eNB or RNC) to optimize RAN parameters and in particular the DRX cycle (i.e. period of discontinuous reception when the UE is in connected state) and the user inactivity timer used in the RAN to release the RRC signaling connection of the user , e.g. during the setup of the subsequent signaling connection (e.g. in the S1-AP Initial Context Setup Request sent to the eNB).

In an embodiment, the RAN may additionally transfer assistance information to the MME or SGSN during the release of the signaling connection (e.g. in the UE Context Release Complete message sent by the eNB to the MME) e.g. the value of the RRC user inactivity timer applied for the signaling connection being released, for subsequent use during the setup of the next signaling connection of the user.

Following steps are illustrated in the example of FIG. 3:

-   -   On-going signalling connection between UE and MME via eNodeB,     -   Expiry of RRC user Inactivity Timer in eNodeB,     -   Message “S1-AP S1 UE Context Release Request” sent by eNodeB to         MME, containing a user inactivity cause,     -   Message “S1-AP S1 UE Context Release Command” sent by MME to         eNodeB,     -   Message RRC Connection Release sent by eNodeB to UE,     -   Message “S1-AP S1 UE Context Release Complete” sent by eNodeB to         MME, containing RAN assistance data for next signalling         connection,     -   MME stores date/time of S1 connection release and RAN assistance         data,     -   New small data available for transmission in UE,     -   Message “NAS Service Request” sent by UE to MME,     -   MME detects frequent transitions between idle and connected         states and notifies so to the eNB,     -   Message “S1-AP S1 Initial Context Setup Request” sent by MME to         eNodeB, containing RAN assistance data and CN assistance data,     -   Radio Bearer Establishment between UE and eNodeB,     -   Message “S1-AP S1 UE Initial Context Setup Complete” sent by         eNodeB to MME,     -   eNB adjusts the RRC user inactivity timer and DRX parameters to         reduce idle-connected transition frequency and optimize battery         usage.

In an embodiment, the MME/SGSN can also monitor the mobility pattern of the user, e.g. by monitoring mobility events (such as handovers, Tracking/Routing Area updates) over time, or thanks to possibly new subscription data (e.g. flagging a static or nomadic user). The MME/SGSN can also use these informations to complement the assistance information passed to the RAN (eNB or RNC), e.g. enabling the eNB to increase the duration during which it maintains a RRC signaling connection w/o user activity for a static or nomadic user (as a handover would be quite unlikely to happen for such a user).

In an embodiment, the MME/SGSN learn the traffic and/or mobility patterns of the user while the user is attached to the network. To minimize impacts in the PS core network, the learned patterns would not be forwarded to the new PS CN node (i.e. MME or SGSN) during inter-CN node mobility, nor stored in the HSS.

Embodiments of the present invention do not require any change in terminals, and are therefore usable with all UEs. Embodiments of the present invention require minimum changes to MME/SGSN while providing potential for large network signaling and UE power battery savings. Embodiments of the present invention do not cause any extra traffic load in the network just for the purpose of learning the user's traffic patterns.

Embodiments of the present invention may be extended with other examples of assistance information. Although it is preferred to rely only on the Mobility Management Control entities, embodiments of the present invention could possibly be extended with assistance information monitored in other PS CN nodes, e.g. the SGW (i.e. anchor point of all the PDN connections of the user under 3gpp access) or PGW, in which case the information would be passed to the RAN either directly e.g. via GTP-U extension headers or via the MME/SGSN (and S11/S4 signalling). The assistance information could then possibly cover e.g. the application type (detected in PGW), inter-packet arrival time (detected in PGW or SGW) . . .

Embodiments of the present invention provide a generic solution for all kinds of applications, simple to implement & deploy, usable with all UEs (i.e. including legacy smartphones), with the potential of significant network signaling (in RAN and CN) and UE power battery savings.

In one aspect, there is provided a method for optimization of network signalling load and/or User Equipment power consumption in a packet mobile system wherein an User Equipment UE has access to a network comprising a Core Network CN accessed by a Radio Access Network RAN.

Various embodiments are provided, which may be taken alone or in combination, according to various combinations.

In an embodiment, CN assistance information is provided by said CN to said RAN for an UE, said CN assistance information including information determined in said CN based on a learning by said CN of a traffic pattern and/or a mobility pattern of said UE.

In an embodiment, CN assistance information provided by said CN to said RAN for an UE is used in said RAN to adjust RAN parameters enabling to control transitions between idle and connected state and/or power consumption in connected state for said UE.

In an embodiment, CN assistance information provided by said CN to said RAN for an UE includes information capable of indicating a potential of frequent transitions between idle and connected state for said UE, and/or information capable of indicating a potential of low or no mobility for said UE, and/or information capable of indicating a potential of mobile originated only traffic or infrequent mobile terminated traffic for said UE.

In an embodiment, RAN assistance information is provided by said RAN to said CN for an UE.

In an embodiment, RAN assistance information provided by said RAN to said CN for an UE includes a current value of RAN parameters enabling to control transitions between idle and connected state and/or power consumption in connected state for said UE.

In an embodiment, RAN assistance information provided by said RAN to said CN for an UE is used in said CN to assist in determining CN assistance information.

In an embodiment, RAN parameters enabling to control transitions between idle and connected state and/or power consumption in connected state for an UE include at least one of: an RRC Inactivity Timer, and a DRX Cycle.

In an embodiment, CN assistance information provided by said CN to said RAN for an UE and indicating a potential of frequent transitions between idle and connected state for said UE, and/or a potential of low or no mobility for said UE and/or a potential of mobile originated only traffic or infrequent mobile terminated traffic, is used in said RAN to increase an RRC Inactivity Timer and/or a DRX cycle for said UE.

In an embodiment, said method comprises:

-   -   a CN entity in charge of control plane learning a traffic         pattern of an UE by monitoring establishment and release of         signalling connections for said UE.

In an embodiment, said method comprises:

-   -   a CN entity in charge of control plane learning a traffic         pattern of an UE by monitoring the time elapsed between the         release of a last signalling connection and the establishment of         a subsequent signalling connection for said UE.

In an embodiment, said method comprises:

-   -   a CN entity in charge of control plane learning a traffic         pattern of an UE by detecting frequent transitions between idle         and connected states for said UE.

In an embodiment, said method comprises:

-   -   a CN entity in charge of control plane learning a traffic         pattern of an UE by monitoring whether or how frequently traffic         originates from the UE or/and the network.

In an embodiment, said method comprises:

-   -   a CN entity in charge of control plane learning a traffic         pattern of an UE by detecting UE that only or mainly utilizes         mobile originated communications.

In an embodiment, said method comprises:

-   -   a CN entity in charge of user plane learning a traffic pattern         of an UE by detecting an application type used by said UE.

In an embodiment, said method comprises:

-   -   a CN entity in charge of user plane learning a traffic pattern         of an UE by detecting inter-packet arrival time for said UE.

In an embodiment, said method comprises:

-   -   a CN entity in charge of control plane learning a mobility         pattern of an UE by monitoring mobility events for said UE over         time.

In an embodiment, said method comprises:

-   -   a CN entity in charge of control plane learning a mobility         pattern of an UE based on subscription data indicating a         mobility profile of said UE, such as static or nomadic user.

In an embodiment, said method comprises:

-   -   a CN entity in charge of control plane notifying CN assistance         information for an UE to a RAN entity.

In an embodiment, said method comprises:

-   -   a CN entity in charge of control plane notifying to a RAN entity         CN assistance information for an UE and RAN assistance         information previously received by said CN entity from a last         RAN entity for said UE.

In an embodiment, said method comprises:

-   -   a CN entity in charge of control plane notifying CN assistance         information for an UE to a RAN entity in a message sent during a         Service Request procedure for said UE, such as in S1-AP S1         Initial Context Setup Request sent by MME to eNB in EPS.

In an embodiment, said method comprises:

-   -   a CN entity in charge of control plane notifying to a RAN entity         CN assistance information for an UE and RAN assistance         information previously received by said CN entity from a last         RAN entity for said UE, in a message sent during a Service         Request procedure for said UE, such as in S1-AP S1 Initial         Context Setup Request sent by MME to eNB in EPS.

In an embodiment, said method comprises:

-   -   a RAN entity, notified of CN assistance information for an UE,         adjusting RAN parameters enabling to control transitions between         idle and connected state and/or power consumption in connected         state for said UE, based on said CN assistance information.

In an embodiment, said method comprises:

-   -   a RAN entity, notified of CN assistance information and RAN         assistance information for an UE, adjusting RAN parameters         enabling to control transitions between idle and connected state         and/or power consumption in connected state for said UE, based         on said CN assistance and RAN assistance information.

In an embodiment, said method comprises:

-   -   a RAN entity notifying RAN assistance information for an UE to a         CN entity in charge of control plane.

In an embodiment, said method comprises:

-   -   a RAN entity notifying RAN assistance information for an UE to a         CN entity in charge of control plane, in a message sent during a         signalling connection release procedure for said UE, such as in         S1-AP S1 UE Context Release Complete sent by eNB to MME in EPS.

In other aspects, there are provided entities configured for carrying out such method, said entities including in particular (though not exclusively), RAN entity (such as eNB for E-UTRAN, or RNC for UMTS), CN entity in charge of control plane (such as MME for EPC, or SGSN for UMTS), CN entity in charge of user plane (such as Serving Gateway S-GW or PDN Gateway P-GW for EPC, or GGSN for UMTS).

A person of skill in the art would readily recognize that steps of various above-described methods can be performed by programmed computers. Herein, some embodiments are also intended to cover program storage devices, e.g., digital data storage media, which are machine or computer readable and encode machine-executable or computer-executable programs of instructions, wherein said instructions perform some or all of the steps of said above-described methods. The program storage devices may be, e.g., digital memories, magnetic storage media such as a magnetic disks and magnetic tapes, hard drives, or optically readable digital data storage media. The embodiments are also intended to cover computers programmed to perform said steps of the above-described methods. 

The invention claimed is:
 1. A method for optimization of network signalling load in an Evolved Packet System (EPS) wherein an User Equipment (UE) has access to a network comprising a Core Network (CN) accessed by a Radio Access Network (RAN), a method wherein CN assistance information is provided by a Mobility Management Entity (MME) to an eNodeB for a UE, and said CN assistance information is used in said eNodeB to adjust eNodeB parameters enabling to control transitions between idle and connected state for said UE, wherein said CN assistance information is notified by said MME to said eNode B in a S1-AP S1 Initial Context Setup Request message.
 2. A method according to claim 1, wherein said CN assistance information includes information capable of indicating a potential of frequent transitions between idle and connected state for said UE, and/or information capable of indicating a potential of low or no mobility for said UE, and/or information capable of indicating a potential of mobile originated only traffic or infrequent mobile terminated traffic.
 3. A method according to claim 2, wherein CN assistance information indicating a potential of frequent transitions between idle and connected state for said UE, and/or a potential of low or no mobility for said UE and/or a potential of mobile originated only traffic or infrequent mobile terminated traffic, is used in said eNodeB to increase an RRC Inactivity Timer for said UE.
 4. A method according to claim 1, wherein said eNodeB parameters include an RRC Inactivity Timer.
 5. A method according to claim 1, wherein said CN assistance information includes information determined in said MME based on a learning of a traffic pattern of said UE, comprising: said MME learning said traffic pattern by monitoring establishment and release of signalling connections for said UE.
 6. A method according to claim 1, wherein said CN assistance information includes information determined in said MME based on a learning of a traffic pattern of said UE, comprising: said MME learning said traffic pattern by monitoring the time elapsed between the release of a last signalling connection and the establishment of a subsequent signalling connection for said UE.
 7. A method according to claim 1, wherein said CN assistance information includes information determined in said MME based on a learning of a traffic pattern of said UE, comprising: said MME learning said traffic pattern by detecting frequent transitions between idle and connected states for said UE.
 8. A method according to claim 1, wherein said CN assistance information includes information determined in said MME based on a learning of a traffic pattern of said UE, comprising: said MME learning said traffic pattern by monitoring whether or how frequently traffic originates from the UE or/and the network.
 9. A method according to claim 1, wherein said CN assistance information includes information determined in said MME based on a learning of a traffic pattern of said UE, comprising: said MME learning said traffic pattern by detecting UE that only or mainly utilizes mobile originated communications.
 10. A method according to claim 1, wherein said CN assistance information includes information determined in said MME based on a learning of a mobility pattern of said UE, comprising: said MME learning said mobility pattern by monitoring mobility events for said UE over time.
 11. A method according to claim 10, wherein: said mobility events include handovers.
 12. A method according to claim 1, wherein said CN assistance information includes information determined in said MME based on a learning of a mobility pattern of said UE, comprising: said MME learning said mobility pattern based on subscription data indicating a mobility profile of said UE, such as static or nomadic user.
 13. A method according to claim 1, comprising: said MME notifying to said eNodeB CN assistance information for said UE.
 14. A method according to claim 1, comprising: said MME notifying to said eNodeB CN assistance information for said UE, in a message sent during a Service Request procedure.
 15. A method according to claim 1, comprising: said eNodeB, notified by said MME of CN assistance information, adjusting said eNodeB parameters based on said CN assistance information.
 16. A method according to claim 1, wherein: said CN assistance information includes information determined in said MME based on a learning of a traffic pattern and/or a mobility pattern of said UE.
 17. A Mobility Management Entity MME, configured to: provide Core Network (CN) assistance information for a User Equipment (UE) to an eNodeB, to be used by said eNodeB to adjust eNodeB parameters enabling to control transitions between idle and connected state for said UE; notify said CN assistance information to said eNode B in a S1-AP S1 InitialContext Setup Request message.
 18. A MME according to claim 17, configured to: notify said CN assistance information in a message sent during a Service Request procedure for said UE.
 19. A MME according to claim 17, wherein: said CN assistance information includes information determined in said MME based on a learning of a traffic pattern and/or a mobility pattern of said UE.
 20. A eNodeB, configured to: receive Core Network (CN) assistance information for a User Equipment (UE) from a Mobility Management Entity (MME), in a S1-AP S1 Initial Context Setup Request message; use said CN assistance information to adjust eNodeB parameters enabling to control transitions between idle and connected state for said UE.
 21. A eNodeB according to claim 20, configured to: receive CN assistance information for an UE in a message sent during a Service Request procedure for said UE.
 22. A eNodeB according to claim 20, wherein: said CN assistance information includes information determined in said MME based on a learning of a traffic pattern and/or a mobility pattern of said UE. 